1. Field of the Invention
The invention relates in general to a wrench having two driving stems pivotally connected with each other. More particularly, this invention relates to a hex key type or Allen wrench having two individual driving stems pivotally connected with each other.
2. Description of the Related Art
A conventional wrench, for example, an Allen wrench, used for gripping and turning or twisting the head of a bolt, a nut, a pipe, or the like commonly typically comprises a one-piece L-shape metal with one end used as the driving stem and the other end used as a handle.
In U.S. Pat. No. 5,943,925, Huang discloses a tool having a foldable structure. The foldable structure disclosed by Huang comprises a coupler pivotally coupled between a driving stem and a handle. Applying the foldable structure to the Allen wrench, the driving stem can be folded in parallel with the handle, that is, with a zero angle relative to the handle. This results in a more compact space for storing the tool. In Huang, with respect to the handle, the driving stem can be rotated from an angle of zero degree to an angle of 180 degree. While turning a bolt in a limited space, for example, around the boundary of two perpendicularly adjoining planes, the handle of the Allen wrench adopting the foldable structure disclosed by Huang can only be turned between zero degree to 180 degrees along a surface perpendicular to the driving stem. When a half circle of the turning action is complete, the user has to disengage the wrench from the bolt. By repositioning the handle to the original point of the turning action, the turning action is repeated until the bolt is fastened as required. In other words, while tightening/untightening a screw, a bolt or a nut in a plane with a limited degree of freedom, a user may need to repeat engaging and disengaging the driving stem to reposition the handle. Moreover, using this conventional structure, there is only one end of the wrench that can be used as the driving tool while the other end is used as a handle only. When a different torque is required, or a screw, a bolt or a nut with different depth is to be driven thereby, a different driving stem has to be connected and reassembled.